6-β-Bromo- and 6-β-iodo penicillanic acid, two novel β-lactamase inhibitors

6-β-bromo penicillanic acid and 6-β-iodo penicillanic acid, two simple penicillanic acid derivatives were compared with clavulanic acid and sulbactam as to their β-lactamase inhibitory properties. Characterized β-lactamase producing strains were used. Generally the two novel compounds were as potent β-lactamase inhibitors as clavulanic acid and inhibited the same range of enzymes. The possibility of β-lactamase inhibitor/β-lactam ester-linked compounds (mutual pro-drugs) is discussed.